Infusion pump devices and systems are relatively well known in the medical arts, for use in delivering or dispensing an agent, such as insulin or another prescribed medication, to a patient. A typical infusion pump includes a pump drive system which typically includes a small motor and drive train components that convert rotational motor motion to a corresponding delivery of medication from a reservoir to the body of a user via a fluid path created between the reservoir and the body of a user. Use of infusion pump therapy has been increasing, especially for delivering insulin for diabetics. Continuous insulin infusion provides greater control of a patient with diabetes glucose levels, and hence, control schemes are being developed that allow insulin infusion pumps to monitor and regulate a user's blood glucose level in a substantially continuous and autonomous manner.
In practice, it is desirable to accurately monitor and control the volume of fluid delivered to the user. However, designing a flow meter or similar component than can accurately cover the entire range of incremental amounts of fluid that may be delivered in a single delivery operation may be costly or problematic once durability, reliability and other constraints are considered. Moreover, the design of the flow meter may be further complicated by the form factor of the infusion device or other packaging constraints. Additionally, depending on the type of pump or fluid delivery technology employed, the flow meter may contact the fluid being infused, which, in turn, may require periodic replacement or disposal of the flow meter or some of its components. Accordingly, there is a need to accurately monitor and control the volume of fluid delivered without compromising device form factor or incorporating a potentially costly flow meter or similar component that satisfies the various requirements that may be imposed.